The one I can recollect most vividly was one of the first HTML tutorial threads.
(Even before "HTML Bootcamp" got started.)
It had circus music going on in the background!
The dang thing was so hilarious it STILL puts a big grin on my face!
But many FReepers had bandwidth and conflict issues with that html command, so it was one of the first to be filtered out by the posting routine.
Drats.
I really did miss out then.
Much like driving someone nuts by using the "marquee" thing.
I always had suspect HTML skills, so I never tried that one.
So I missed out on scrolling the thread.